The present invention relates to a system (method) for retrieving secure information from a database for temporary storage and usage by an information user.
Systems for storage and retrieval of secure information are well known in the art. As used herein, the term "secure information" is intended to mean information (alphanumeric data, graphics and the like) which is either encrypted or otherwise protected to prevent access thereto except by an authorized user. Such systems have been proposed and are employed both for the case where the information source (database) is centralized, and for the case where the information source has been distributed to multiple users. In the latter case, CD-ROMs have been used to export databases to multiple users so that information storage and retrieval takes place at the user site.
In the U.S. Pat. No. 5,010,571 to Ron Katznelson and the U.S. Patents Nos. 4,827,508, 4,977,594 and 5,050,213 to Victor Shear, it is proposed to provide encrypted digital information on CD-ROMs at the user site and to monitor and account for each item or "packet" of information which is retrieved and decrypted from a CD-ROM by an authorized user.
This concept of retrieving information on a "pay-as-you-go" basis is also disclosed in the U.S. Pat. No. 5,247,575 of Peter J. Sprague and Thomas H. Lipscomb to include encrypted data which is "broadcast" to multiple user sites from a central source and to permit individual access to encrypted data at a central source, as required, using conventional time sharing techniques and transmission via telephone dial-up or local area network (LAN) or wide area network (WAN) communication.
All of these prior art systems permit the user's access to the secure information to be monitored and strictly controlled. However, once the information has been decrypted and made available to the user, the user has access to it indefinitely and can reproduce it any number of times.
The problem of copying cleartext information is a familiar one to information providers. For example, the publisher of a trade journal or magazine well knows that a single issue or subscription will be circulated among a large number of readers and each reader may and in fact, does, photocopy one or more articles for further distribution to multiple readers. As a result, the information provider must set an artificially high subscription fee since the number of paid subscriptions to the trade journal represents only a small fraction of the total number of readers of articles in this journal.
Clearly, legal restrictions based on the copyright law are not effective to curb and protect against unauthorized copying of the published information.
With secure information provided electronically to an information user, it is possible to insert a "virus" in the data stream which causes the information to automatically self-destruct, or at least be made unreadable, after a given date or a given length of time. This technical solution to the problem of copying cleartext information is not wholly satisfactory because, at best, it places artificial temporal limits on the user and, at worst, the "virus" itself can be attacked and destroyed by appropriate technical means.